Anatomical wood variation of Buddleja cordata (Buddlejaceae) along its natural range in Mexico

ABSTRACT Complex gene regulatory circuits exhibit emergent properties that are difficult to predict from the behavior of the components. One such property is the stability of regulatory states. Here we analyze the stability of the lysogenic state of phage λ. In this state, the virus maintains a stable association with the host, and the lytic functions of the virus are repressed by the viral CI repressor. This state readily switches to the lytic pathway when the host SOS system is induced. A low level of SOS-dependent switching occurs without an overt stimulus. We found that the intrinsic rate of switching to the lytic pathway, measured in a host lacking the SOS response, was almost undetectably low, probably less than 10−8/generation. We surmise that this low rate has not been selected directly during evolution but results from optimizing the rate of switching in a wild-type host over the natural range of SOS-inducing conditions. We also analyzed a mutant, λprm240, in which the promoter controlling CI expression was weakened, rendering lysogens unstable. Strikingly, the intrinsic stability of λprm240 lysogens depended markedly on the growth conditions; lysogens grown in minimal medium were nearly stable but switched at high rates when grown in rich medium. These effects on stability likely reflect corresponding effects on the strength of the prm240 promoter, measured in an uncoupled assay system. Several derivatives of λprm240 with altered stabilities were characterized. This mutant and its derivatives afford a model system for further analysis of stability.

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Hymenoscyphus fraxineus (ash dieback).

10.1079/cpc.108083.20210104833 ◽

2021 ◽

Author(s):

Jessica Needham ◽

Joan Webber

Keyword(s):

North Africa ◽

Fungal Pathogen ◽

The Other ◽

New Disease ◽

Ash Dieback ◽

South West ◽

Hymenoscyphus Fraxineus ◽

Natural Range

Abstract H. fraxineus is an anamorphic fungal pathogen that causes ash dieback. Due to the severity of ash dieback H. pseudoalbidus has been on the EPPO Alert list since 2007. It is not known what caused the emergence of this 'new' disease (NAPPO, 2009). Its spread in Europe is thought to be mainly by ascospores, but infected nursery saplings may carry the fungus to new areas. The entire natural range of known hosts, including North Africa, Russia and south-west Asia (USDA-ARS, 2009), is currently threatened by ash dieback, with large areas already affected (Pautasso et al., 2013). Little is known about the susceptibility of the other species of ash in temperate zones.

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An eco-evolutionary rationale to distinguish alien and native status: why the dingo is a native species on mainland Australia

Australian Zoologist ◽

10.7882/az.2021.039 ◽

2021 ◽

Vol 41 (3) ◽

pp. 358-366

Author(s):

Peter B. Banks

Keyword(s):

Alien Species ◽

Introduced Species ◽

Native Species ◽

Genetic Basis ◽

Evolutionary Approach ◽

Range Transport ◽

The Status ◽

Local Species ◽

Natural Range ◽

Native Status

Distinguishing between whether a species is alien or native can be problematic, especially for introduced species that are long-established in new areas outside of their natural range. Transport by humans is the criterion for alien status used by many definitions, whereas arbitrary time since arrival to a location is often used to define native status. Here I propose an eco-evolutionary approach to distinguish between alien and native status and use this to resolve uncertainty in the status of the dingo in Australia. Dingoes were transported to mainland Australia by humans, but more than 4000 years ago, and dingoes now interbreed with feral domestic dogs. Legally, this mix of events has the dingo classified as native in some jurisdictions and alien in others. I suggest that native status for introduced species should be based on (1) whether the species has evolved in their new environment; (2) whether local species recognise and respond to them as they do towards deep endemic native species, and; (3) whether their impacts benchmark against those of a native species or are exaggerated like those of other alien species. Dingoes are behaviourally, reproductively and morphologically different to close ancestors from south-east Asia, and this difference has a genetic basis indicative of evolution in Australia. There is abundant evidence that native prey species on mainland Australia recognise and respond to them as a dangerous predator, which they are. But there is strong evidence that dingo impacts on prey are not exaggerated, with effect sizes from mensurative experiments similar to those of experiments on native predators rather than alien predators. These three lines of evidence suggest dingoes should be considered native to mainland Australia. I suggest this eco-evolutionary approach to defining native status can be helpful in resolving the often-heated debates about when an alien species becomes native.

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Modelling the effects of inter-observer variation on colour rendition

Lighting Research and Technology ◽

10.1177/1477153517744387 ◽

2017 ◽

Vol 51 (1) ◽

pp. 37-54 ◽

Cited By ~ 2

Author(s):

MJ Murdoch ◽

MD Fairchild

Keyword(s):

Colour Vision ◽

Spectral Characteristics ◽

Observer Variation ◽

Light Sources ◽

Standard Observer ◽

Natural Range ◽

Normal Colour ◽

Range Of Variation

The colour rendition characteristics of light sources are quantified with measures based on CIE standard observers, which are reasonable representations of population averages. However, even among people with normal colour vision, the natural range of variation in colour sensitivity means any individual may see something different than the standard observer. Modelling results quantify the effects of these inter-observer differences on colour rendition measures defined by IES TM-30-15. In general, inter-observer differences tend to be smaller for light sources with high colour fidelity values, and they are affected by spectral characteristics of different lighting technologies. The magnitude of variation in colour rendition measures, up to 5–10 units in IES TM-30-15 ( Rf, Rg), measures is compared with other sources of variability and ambiguity.

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